An interceptor rocket motor insulation system is typically based on a hydrocarbon prepolymer such as ethylene-propylene-diene monomer (EPDM), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), or polyisoprene (PIP) rubber. Reinforcement fibers such as silica or Aramid (e.g; aromatic polyamide fiber, an example is poly-p-ethylene terephthalamide with trademark Kevlar) are incorporated prior to cure to provide strength and thermal characteristics. The high viscosity of hydrocarbon elastomeric gumstock resins somewhat limit the type reinforcing fibers selected for use to those which are tough and to those fibers which can be satisfactorily incorporated into the high viscosity resin. Additionally, hydrocarbon-based insulations require the incorporation of various modifiers, such as, plasticizers, stabilizers, softeners, etc., before hydrocarbon gumstock can be satisfactorily used in insulation forming and curing. In other words, the chemistry required for using hydrocarbons for insulation material is quite complex and places certain limitations on the system where used.
The requirements for interceptor motor insulation system dictate the need for an insulation system thermal characteristics while also being inert toward various propellant compositions. An extrudable material for ease of application and an insulation material which has superior characteristics in modulus, tensile strength, elongation, and stability in Shore A hardness properties when aged at elevated temperatures and when aged in air at elevated temperatures is a desirable material for use in interceptor motors.